This invention pertains to sewer check valves or backup valves and particularly to check valves having means for applying mechanical pressure to ensure tight closing. In addition, the present valve has a sharp cutting edge at the valve seat.
Check valves that have respective flaps to cover smooth seals about the inlets resulting from pressure of backup sewage are commonly used. Even though pressure against the flaps applied from the backup may be substantial, nevertheless, the valves often fail to prevent backup of sewage into basements. Failure is likely because heavier materials in sewage lodge between the mating seals and prevent full closure of the valves, especially when only the pressure of the backup is forcing the flap against the inlet seal.
As shown in U.S. Pat. No. 3,817,278 issued to Robert E. Elliott on June 18, 1974, spring pressure is used to control closure of check valves in gas lines. However, the spring pressure is usually adjustable because the tension of the spring is related to the pressure of gas within the valve. A valve with both seals being V-shaped is shown in U.S. Pat. No. 1,687,860 issued to G. S. Fosnaugh et al on Oct. 16, 1928. This valve is a slush-pump valve rather than a check valve and reciprocates with the pump in the system with which it is connected to grind small objects such as small pieces of rock. The entire V-shaped surface of one of the seats fitting closely within the surface of the other seat suitable for grinding rocks does not provide an unobstructed sharp edge for cutting chunks of sewage in backup valves.